A Tree-Based Remediation System for Treatment and Hydraulic Control of a Hydrocarbon Plume in a 20 Foot Deep Aquifer at a Former Refinery in Central Oklahoma  Edward Gatliff, Ph.D. – Applied Natural Sciences, Inc  Brad Snow, PE, PG – Snow Environmental Solutions, LLC

 The Problem  Possible Solutions  Site Conditions  Feasibility (Pilot Study)  Results and Lesson Learned  Selected Solutions Phyto-Integrated™ Remediation System Approach

The Problem Former Refinery with Petroleum Contaminant Plume Migrating Off-Site Benzene Plume >350 acres above MCL Mostly 1 to 10 mg/L Off-site impacts

Possible Solution Using Trees for Full-Scale Hydraulic Control  Minimum groundwater extraction rate Darcy’s Law for natural flow rate: function of transmissivity, hydraulic gradient, plume width = 20,000,000 gallons/year, natural flow = 38 gallons/minute  Design basis for tree extraction rate at full canopy 36 inches/year = 1.9 gpm/acre At 30 ft. spacing, 56 gpd/tree average over year 20 acres of trees minimum required

 Conduct Pilot Study to determine the feasibility of using a TreeWell ® system - a Tree-Based Pump and Treat system Evaluation of Integrated-Phyto Approach

 Alternative to Traditional Pump and Treat System  Tree acts as solar pump  Capillary groundwater moves upward through soil column & rhizosphere as the tree transpires  Significant biodegradation occurs in the soil column (bioreactor effect and reduced phytotoxicity) Patented TreeWell ® Approach

Site Conditions Alluvial Terrace Deposits  Water table Ft BGS  ~0-25 Feet Upper confining clay  ~25-40 Feet Sand unit K avg = 2 x cm/sec Confined aquifer – water levels rise into overlying clay  Lower confining red bed mudstone

Climate also a challenge for Trees Heart of the Dust Bowl  High Temperatures Common Often Weeks of 100F+ Temperatures  Drought conditions common  Impractical to irrigate

 Determine ability to establish trees without irrigation in the presence of LNAPL (phytotoxicity) have roots draw water from 20 foot deep  Evaluate tree species for viability Weeping Willow Hybrid Poplar London Plane (Hybrid Sycamore) Pilot Study Feasibility of Utilizing TreeWell System

TreeWell System Successfully Applied Elsewhere

Pilot Study Five Study Areas  One Background (no VOCs)  One Main – hydraulic effect  Two LNAPL (3 ultimately) – toxicity effects  One Lysimeter – water use

Site TreeWell Unit Design  40 inch hole bored to feet into Sand Aquifer  Liner placed to 15 ft bgs (near top of GW in 2012 & 2015)  Aeration tubing looped to 15 ft bgs  Entire column filled with clean rooting media

Pilot Study – June 2013

 Trees can be grown in TreeWell system without irrigation (even in very harsh climatic conditions)  London Plane proved most hearty  With pesticide management, Hybrid Poplar also viable  Golden weeping willow replaced with Black Willow  Roots readily develop to top of capillary fringe (which was found to rise feet above water table creating a significant bioreactor column)  Significant soil gas venting likely reduces potential phytotoxic effects Pilot Study - Results

Roots Develop to Capillary Fringe Root Development & Soil Moisture by Depth Roots to 11 feet (Capillary Fringe) Water ~22 Feet BGS

 A recent soil gas study at another TreeWell system location yielded results that showed the TreeWell units acting as vents for soil gases  Soil VOC gases were not present in sample ports near TreeWell units Soil Gas Venting by TreeWell Units

Soil gas Venting by Site TreeWell Units A Thermo Scientific TVA FID unit was used to measure VOC concentration of soil gases emerging from the TreeWell aeration tubing.  To enhance air exchange in the looped aeration tube one side is placed at a higher elevation than the other - creating a venturi effect  Both the “intake” and “outflow” vents were tested Note: intake vents typically zero

Soil Gas Venting mph Each TreeWell unit was tested on a daily basis from 11/4-15, 2014

Soil Gas Venting mph Soil gas emissions subside with no wind to enhance venturi effect

 How to install 40 inch diameter, feet deep TreeWell units more safely & efficiently Safety Platform placed over the hole Pilot Study Lessons Learned

 Treat LNAPL Pockets with Oxygen Sparging  Reduce hydraulic gradient with Pump & Treat system creating opportunity for Monitored Natural Attenuation to control off-site migration of contaminant plume  Use TreeWell ® system as a Tree-Based Pump and Treat system to reduce hydraulic gradient Selected Solutions

Treat off-site LNAPL pockets with oxygen sparging

Natural Attenuation is dependent on travel time

Install 400 Trees Reduce On-Site Gradient to Achieve Hydraulic Effect in trees extracting an average of 50 gallons per day could achieve the necessary reduction in the hydraulic gradient and thus the travel time of the contaminant plume through the area of most concern

Benefits  Integrated-Phyto Approach offers significant cost savings over traditional Pump and Treat. Overcomes significant problems encountered with Pump & Treat system (clogged pipes, wells, iron precipitates, etc…) Low O&M Savings - Conservative Estimate of over $2 million over a 30 year period

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